Disclaimer - As a CTO of a company I have to take a stance on these issues. As a matter of fact, as you raise money, part of the due diligence is to audit the libraries that you use to make sure that you don't use libraries that can jeopardize the future of the company.

Using an AGPL library for a Saas company will be flagged as a risk by lawyers during the due diligence process.

At Truework, we love open source and try to contribute when we can, but the reality is that if a library is AGPL, I'll ask my team to not use it. It's just not worth it to risk so much for a single library. Yes, it's unlikely that you will have to go to court because you use that one library, but if you do... well that's bad news for you.

If you build a business, it's about making sure that there there is a reasonable ROI for risks that you take. APGL tilts the balance towards "we shouldn't use this, it's too risky". Make your own decisions, but keep that in mind.